The computing landscape has also been changed by the increasing deployment of distributed computing and storage in scientific computing and enterprise information networks. Today's high performance scientific, load balancing and high availability clusters typically are comprised of heterogeneous collections of PCs and servers sharing hierarchical storage with caches, local and remote main memory, secondary and tertiary (for backups) storage configured as a storage area network (SAN). This distributed hardware configuration offers many benefits such as higher performance, scalability and resilience. While such configurations are cheaper to deploy than previously available supercomputing or RAID-based storage solutions, the cost of the Fiber Channel switches in the network fabric that ties the processors and storage puts them out of reach for many small enterprises and scientific research groups. Furthermore, larger clusters with several switches can be difficult to deploy, maintain and reconfigure.
The static nature of Fiber Channel topologies may also have a detrimental effect on system performance. Specifically, the mismatch between access times of secondary storage and processor speeds, coupled with widely different application I/O access patterns, adversely affect the performance of these systems. Researchers and designers have addressed these problems in the past by improving parallel I/O and storage and optimizing I/O requests. I/O optimization often produces dynamic connectivity requirements that depend on the tasks at hand. Static network topologies offer sub-optimal emulations of these changing connectivity patterns.
As a result, recent years have witnessed the emergence of wireless local area networks (WLANs). WLANs are convenient: they allow flexibility and roaming and support dynamic environments. Furthermore, they are easy to install. In some cases, e.g., older buildings, they may be cheaper to deploy: an entire network can be put together in a matter of hours rather than days with no need for wiring or rewiring. Several studies have shown that in many scenarios, WLAN have a lower cost of ownership than their wired counterparts despite the potentially cheaper cost of wired LAN cards.
However, current wireless interfaces do not typically provide the same bandwidth as that available in their wired counterparts. In addition, studies have shown that TCP performance is severely degraded when the wireless link experiences high bit error rates, e.g., when the receiver and transmitter are distant. This degradation is mainly due to the fact that TCP assumes that congestion, rather than unreliable communication at the physical layer, causes packet losses and delays. The mechanisms used by TCP to handle congestion (e.g. reducing the TCP window size) result in a reduction of end-to-end throughput in wireless networks that can dramatically impact the utilization of the precious bandwidth available.
As a result, there is a need in the art for the present invention.